This invention relates generally to loading dock leveler assemblies and more particularly to a dock leveler assembly which when in one mode automatically provides a barrier to prevent material handling equipment from accidentally running off the exposed front end of the loading dock.
Loading dock levelers, sometimes called dockboards, are used to facilitate the loading and unloading of variously sized vehicles which are parked adjacent to a loading dock that has a working surface above the roadway adapted to adjoin the bed of a parked vehicle. Examples of loading dock leveler assemblies are disclosed in U.S. Pat. Nos. 3,583,014, 3,699,601, 3,728,753, 4,110,860, 4,257,137, 4,531,248, 4,570,277 and 4,744,121. Such dock levelers compensate for height variations between the bed of the parked vehicle and the working, sometimes referred to hereafter as platform surface, surface of the dock since they are typically disposed in a pit or recess at the front of the loading dock and include a ramp pivotal between a raised position above the working surface of the dock and a below dock level position. An extension plate or lip is hinged to the front edge of the ramp and is movable to an extended position to span the gap between the bed of the parked vehicle and the front edge of the ramp. When such dock levelers are not in use, they are stored in a cross-traffic position having an exposed upper surface of the ramp flush with the working surface of the dock and the lip disposed in a depending position.
In the practical implementation of such dock levelers certain safety problems may arise. Loading dock personnel may accidentally drive or push fork lift trucks or related material handling equipment off the exposed front end of the dock leveler when there is no vehicle parked adjacent the loading dock and the dock leveler is stored in the cross-traffic position.
Dock levelers have heretofore been provided to minimize the risk of such accidental run off. Such dock levelers utilize a lip pivotally fixed to the front edge of the ramp wherein the pivot axis of the lip is set outwardly, or forwardly, a substantial distance from the rear edge of the lip. Such a design allows the rear section of the lip between the pivot axis and the lip rear edge to project above the ramp surface and form a barrier when the lip is not in its fully extended cantilevered position. When such a lip is in positions between the stored depending position and the fully extended cantilevered position, the rear section of the lip still forms a barrier by projecting angularly to a varying degree above the ramp surface. Thus, the continued projection of the lip rear section might seriously obstruct loading and unloading operations.
Another type of dock leveler having an automatic vehicle barrier is disclosed in U.S. Pat. No. 4,920,598. The dock leveler assembly disclosed therein relies on a portion of the lip to form a barrier.
There are circumstances where it is desirable to provide an automatic barrier to prevent accidental material handling equipment runoff when the dock leveler assembly is in a stored cross-traffic position and loading and unloading equipment is being utilized. Such circumstances include situations where material must be loaded onto or unloaded from the extreme rear of the bed of the vehicle parked adjacent the loading dock and the placement of the material interferes with the use of the dock leveler with the lip thereof in a fully extended position resting on the rear of the vehicle bed. It is also advantageous to avoid the pinching area developed in levelers which utilize a lip having a barrier forming rear section which overlaps the ramp under certain operating conditions since a potential for entrapping equipment or personnel exists in such levelers.